A couple of possibles could be Vinca (perriwinkle) or Hypericum (Rose of Sharon). The first is low growing and can become a nuisance if it gets out of control and has blue flowers. The second is taller and has yellow flowers.

I have been trying to cultivate a bank of the same description since a groundworker with a digger, with no horticultural skill,BUT.. the relative of the property owner, charged an arm & a leg to dispense of the gorse at the wrong time of year,spread & buried the seeds far & wide,then planted hundreds of pounds worth of mainly unsuitable shrubs,with instructions for his family member to water them if the weather was hot,before making off with his wad of cash! Nothing takes or grows rapidly in sandrock ground (except those things that have established & reproduced grrr!) my main battle has been getting rid of these without damaging the few shrubs left struggling for life. Funnily enough a separated & discarded hypericum is the only thing I've planted thus far Bulbaholic! The key is to put LOTS of moisture retaining compost in pre dug holes where the roots are to go,& put in bits of upright plastic drainpipe or bottles cut off at the bottom close to where the rootball will be,picking a day when the ground isnt too dry (as I'm sure you know what happens!) Only when youve got the plant in can you water via the pipes etc in situ..& water in LOTS,then regularly,even in wet weather. Apart from the said hypericum which is doing ok, I'm working on getting some test case contoneaster varieties in,& soon, from the dozens of cuttings I've taken & grown on,not forgetting some bonemeal,or the feed in Spring. Hoping these will create ground cover,+ self setting berries once they eventually take off..well,ones the birds dont take.

Cotoneaster dammeri is a good one for banks as it trails along the ground and roots as it goes along. Try other scramblers such as variegated ivies.

I also like Cotoneaster congesta, a real ground hugger. It follows the contours like a pair of tight trousers and you can even walk on it.

Oops..misread that initially as 'like a pair of tight trousers you can even walk in'...not on steep slopes I wouldnt Bulbaholic,ha. Loose bags for me every time! Good Cotoneaster suggestions both,thanks. Think I may have some of the congesta coming on for planting, but the dammeri sounds useful too Voluneer. The benefit of it's additional rootage would help in keeping the bank stable. As Nomad would I'm sure agree,sand rock ground makes no attempt to defy gravity,& the least disturbance will have what should be at the top, right down to ground level,bringing as much of the middle bit with it as possible. Another reason I was dismayed at seeing the well established gorse roots ripped out on the bank I'm trying to salvage. Another useful tip is to make a terraced path spanning the slope so that any work can be done safely without disturbing the ground from trying to keep your footing. Good luck Nomad.

Thank you all for your advice. It has been most useful.
That said, my wife (who has many years experience and is the real gardener around here) suggested Hypericum at the outset - so that fits in well with what you all suggested.
That said, she has an RHS Gardening Encyclopaedia in which it says that Hypericum, Vinca (which is probably the most attractive) and Cotoneaster should all be planted in full sun, which is most certainly not the case here. (We have a Cotoneaster which faces east and is in full sun and is positively thriving on it!)
It's all very confusing...
We'll have a long hard think about it - but that you all again for your contributions.
Regards,
Nomad

Whilst cotoneaster prefers sun to flower and berry nicely it will grow as a green cover in shade. I have seen both hypericum and vinca preforming very nicely in deep shade.

Vinca is routinely suggested for shady sites. Major spreads more quickly, minor grows more densely - try both in different places to see which does best. There are blue ones and white ones. Hypericum is fine and tough, but I think the dead flowers look a mess and on a large bank you wouldn't want to keep deadheading them.